Race Demon questions

It's not that they're rated 'smaller', they were wet-flow rated as opposed to other brands(holley). It gets way more technical but the quick and dirty is that a wet-flowed 750cfm carb has a real-world flow capability about equal to a larger carb that was dry-flowed. If I remember the difference for gasoline was somewhere around an 8% difference and quite a bit higher for alcohol(approximately double maybe). As far as the 'idle-eze' jet down in the carb base, I have no idea why someone would plug it when you can just screw it closed, unless someone stripped some threads. Easy enough to pull the basepate off and inspect it. They are nice for pulling a little extra air ar idle without opening the blades too much(or drilling) if your engine needs it. Now just my opinion, but a 750 flow rated any whichaway ain't gonna cut it on a performance 500 cube engine. It'll work, just won't be optimal. I use an older 850 demon on a mildly built 440+.060 and once I got it all dialed, added adjustable bleeds etc it kicks the crap out of the 750 QF that I have. The QF was great once tuned in, a good unit, but the big demon is just performing better and I feel it when driving. It is a bit more finicky though especially in colder (CA lol) weather but I don't mind..